1. Field of the Invention
This invention relates to a preheating device for a combustible air and fuel charge, particularly for a charge aspirating internal combustion engine.
2. Description of the Prior Art
The prior art has long recognized the advantages of heating a fuel and air charge while it is being drawn into a piston type internal combustion engine to insure vaporization of the liquid fuel portion of the charge. The need for such preheating was particularly keen when heavy oils were used as fuels for such engines, but is was also claimed that engines utilizing more volatile petroleum distillates such as gasoline could benefit from using a preheater for the intake charge.
Examples of early patents disclosing such inventions are seen in British Specification No. 104716, published in 1917; U.S. Pat. No. 1,122,038 issued in 1914; U.S. Pat. No. 1,132,420 issued in 1915; and U.S. Pat. No. 2,090,823 issued in 1937. More recent examples are seen in U.S. Pat. Nos. 3,498,279, 3,645,243 and 3,792,688.
The foregoing patents, as well as numerous other patents and publications, reflect the belief on the part of experts in this field of technology that heating a fuel and air charge while it is aspirated by an engine helps to completely vaporize the liquid fuel supplied to the engine, with consequent improvement in efficiency of the engine. Since combustion efficiency is improved, less fuel is required to satisfy the power demand of the engine. Moreover, since the heat supply for the preheater may be provided by the waste heat from the engine, additional energy input is not necessarily required to operate such preheaters. Many versions of preheater arrangements have thus far been proposed, yet it is apparent from observing modern energy conversion engines that the results obtained from the prior art devices have not met expectations. Many modern engines, of course, are arranged to preheat the charge formed in the carburetor by means of heated intake manifolds that are part of the engine assembly and which are heated in various ways by exhaust gases or engine coolant. The temperature of the incoming fuel/air charge in such installations is raised to some extent, depending upon engine operating conditions. However, the ability of the intake manifold to smoothly deliver a charge of fully vaporized fuel without unduly reducing the density of the charge under all operating conditions is sometimes less than ideal.
The present invention has as its objective the overcoming of problems and shortcomings of prior art charge preheating and vaporizing devices, and proposes a device and process that is believed to provide distinct advantages for modern gasoline powered internal combustion engines.